(CBS) -- Among the strongest evidence in George Zimmerman's defense
may be George Zimmerman himself, several experts say - in part, because
it may prove difficult for prosecutors to refute his claim that he
killed Trayvon Martin in self-defense.

Zimmerman,
a former neighborhood watch captain, is charged with second-degree
murder in the shooting death of the teen during an altercation in
February 2012 in Sanford, Florida. His case is set to go to trial Monday,
June 10.

"There's only two people who know exactly what
happened, and one of them is no longer alive," said Florida criminal
defense attorney Brian Tannebaum, president of the Florida Association
of Bar Defense Lawyers and past president of the Florida Association of
Criminal Defense Lawyers. "It's a hard burden when Zimmerman is going to
say, 'Listen, I was in fear, I got into a fight with this kid, I didn't
know him, I didn't know what he was going to do.' What is out there to
dispute what he's saying? That's the difficult part."

Jose
Baez, lead defense attorney for Casey Anthony, who was acquitted of
murder, said he doesn't believe the prosecution can prove beyond a
reasonable doubt that Zimmerman's story isn't true.

"The
state is going to have a hard time refuting the claim of self defense-
that's where the case can easily be won by the defense," Baez said. "The
state not only has to put forward their evidence, they have to exclude
every reasonable hypothesis of innocence and do so beyond a reasonable
doubt - I don't think they can."

The defense will likely
point to evidence including the photos of Zimmerman bleeding from the
head following the altercation to corroborate his story, Tannebaum said.
Though it's not clear whether the 29-year-old will take the stand in
his defense, experts say they believe it's likely.

"Unless
the state makes the argument that [Zimmerman's injuries] were
self-inflicted, they clearly occurred through some kind of altercation,"
Tannebaum said."If Zimmerman is going to testify and say Trayvon Martin
assaulted me and I was in fear for my life, that would be a big piece
of evidence."

What exactly happened in the Retreat at
Twin Lakes gated townhome community on the night of Feb. 26, 2012 - and
who started the altercation - will certainly be at issue throughout the
trial. But it's less clear whether either side will attempt to paint a
picture of Martin's personality for the jury.

Zimmerman's
defense team recently released a series of photos in which Martin, 17,
is seen blowing smoke and making obscene gestures, as well as text
messages in which he talks about fighting, smoking marijuana, being
suspended from school and being kicked out of his mother's home.

Though
Seminole County Circuit Judge Debra Nelson ruled at a May 28 pre-trial
hearing that jurors would not hear details of Martin's alleged past drug
use and fighting or suspension from school during opening statements,
the defense may still be able to introduce some of the evidence at trial
if they prove to her its relevance.

At the hearing,
Zimmerman's attorney Mark O'Mara told the judge that Martin's alleged
marijuana use and past fighting were central to the self-defense
argument.

"We have a lot of evidence that marijuana use
had something to do with the event," O'Mara said at the hearing. "It
could have affected his behavior."

The defense may push
to use the evidence in an attempt to demonstrate to jurors that
Zimmerman had reason to feel his life was in danger, Tannebaum said.

"An
unarmed black kid in the area is not a legal reason to fear for your
life," Tannebaum said. "They will want to get in every piece of evidence
they can that will cause the jury to believe that George Zimmerman was
in fear."

Also at issue is the significance of several
key 911 calls in which a state audio expert claims Martin is heard in
the background saying, "I'm begging you." Other experts have said the
shouts were a mix of Martin and Zimmerman.

The judge is scheduled to rule at a June 6 hearing on whether the state expert used scientifically acceptable techniques, the Orlando Sentinel reports.

In
another recording that some have speculated could be damaging for the
defense, Zimmerman calls 911 to report a suspicious person, and tells
the dispatcher he is following the teen.

Baez, however, says the fact that Zimmerman himself called 911 may actually lend weight to his self-defense claim.